Wireless communications systems are increasingly using multi-mode and multi-band transceivers to increase the data transmission capabilities of wireless communication devices. The output power of signals transmitted by these multi-band transceivers may be regulated by one or more power amplifiers included in the transceivers. These power amplifiers may amplify the output power as a function of a bias voltage applied to the power amplifiers. As the amount of bias voltage increases, the amplification or gain of the amplifier may increase. However, when the bias voltage reaches a certain level, increases in the bias voltage may result in little to no increases in the gain. When the amplifier reaches this state, the amplifier may be referred to as being in a saturation state or operating in saturation. While operating in saturation, the bias voltage may continue to increase while the amplifier gain only nominally increases. Therefore, when the power amplifier is operating in saturation although the bias voltage may increase, the signal power amplified by the power amplifier may plateau and reach its maximum level. This increase in bias voltage may cause the amplifier to increase its power consumption, which may reduce the battery life of the battery associated with the wireless communication device that includes the amplifier without providing any benefit, such as increased signal power.
Further, when the power amplifier operates in saturation the power amplifier may not deliver signal power in response to changes in the bias voltage or input signal power. In such instances, the mobile device may not reach the desired power level. Further, when the power amplifier is operating in saturation, the mobile device cannot respond to power control commands from the base-station. Moreover, during saturation, the transmit power control accuracy may degrade and may fail to meet network power vs. time specifications. Additionally, during saturation the power amplifier may not shut down and will degrade transient spectrum specifications due to sudden ramp down.
Additionally, as multi-mode and multi-band transceivers are used, the signals being transmitted by the transceivers may experience interference from on channel signals or co-band signals. These interfering signals may be referred to as “blockers.” The interferer signals (blockers) may be external signals that may be from an adjacent channel user operating in another mobile protocol. For a mobile device operating in Wideband-Code Division Multiple Access (WCDMA) mode, an example of a blocker can be a Global System for Mobile Communications (GSM) mobile device, a Wireless Local Area Network (WLAN), a Bluetooth or a global positioning System (GPS) device. The blockers may cause the transmitted signals to not reach their intended destination and/or may render the signals unreadable.